Chrysapace Crawley, 1924a

Borowiec, Marek L., 2016, Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae), ZooKeys 608, pp. 1-280 : 90-93

Taxon classification Animalia Hymenoptera Formicidae

Chrysapace Crawley, 1924a gen. rev.

Type-species.

Chrysapace jacobsoni , by monotypy.

Chrysapace is the only extant doryline genus also known from Baltic amber (late Eocene). These ants are extremely rarely collected and no observations of their biology have ever been published.

Diagnosis.

Worker. The workers of this lineage are recognizable by a combination of prominent costate sculpture present on most of body surface, large eyes, exposed antennal sockets, two spurs on mid and hind tibiae, and pretarsal claws with a tooth. The New World Cylindromyrmex are the only other dorylines that have two pectinate tibial spurs and strongly costate or rugose sculpture but they are recognized by at least moderately developed antennal scrobes and horizontal torulo-posttorular complex that partly conceals antennal sockets. In Chrysapace there are no scrobes and antennal sockets are fully exposed.

Male. The males share the characteristic spur formula with the workers, have a well-defined groove on the mesopleuron, two submarginal cells, the marginal cell enclosed by R·f1 and Rs·f4-5, and pretarsal claws armed with a tooth. Acanthostichus and Cylindromyrmex can have similar wing venation. The former has only one pectinate tibial spur on each mid and hind tibiae and the latter has no transverse groove on the mesopleuron and simple pretarsal claws. Males attributed to Procerapachys also have similar wing venation but only a single tibial spur and no transverse groove on the mesopleuron.

Description.

Worker.Head: Antennae with 12 segments. Apical antennal segment moderately enlarged, broader than and about equal in length to two preceding segments combined. Clypeus without cuticular apron. Lateroclypeal teeth absent. Parafrontal ridges reduced. Torulo-posttorular complex vertical. Antennal scrobes absent. Labrum with median notch or concavity. Proximal face of stipes projecting beyond inner margin of sclerite, concealing prementum when mouthparts fully closed. Maxil lary palps 5-segmented. Labial palps 3-segmented. Mandibles triangular, with teeth. Eyes present, composed of more than 20 ommatidia. Ocelli present. Head capsule with differentiated vertical posterior surface above occipital foramen. Ventrolateral margins of head without lamella or ridge extending towards mandibles and beyond carina surrounding occipital foramen. Posterior head corners dorsolaterally immarginate or marginate. Carina surrounding occipital foramen ventrally present. Mesosoma: Pronotal flange separated from collar by distinct ridge. Promesonotal connection with Pronotomesopleural suture completely fused. Pronotomesopleural suture visible, unfused up to notal surface. Mesometapleural groove replaced by cuticular ridge. Transverse groove dividing mesopleuron absent. Pleural endophragmal pit concavity absent. Mesosoma dorsolaterally immarginate. Metanotal depression or groove on mesosoma absent. Propodeal spiracle situated low on sclerite. Propodeal declivity with or without distinct dorsal edge or margin and rectangular in posterior view. Metapleural gland without bulla visible through cuticle. Propodeal lobes present, well developed. Metasoma: Petiole anterodorsally marginate, dorsolaterally immarginate, and laterally above spiracle immarginate. Helcium in relation to tergosternal Pronotomesopleural suture placed at posttergite and axial. Prora forming a V-shaped protrusion. Spiracle openings of abdominal segments IV–VI circular. Abdominal segment III anterodorsally marginate, dorsolaterally immarginate. Abdominal segment III more than half size of succeeding segment IV, which is weakly constricted at presegmental portion (uninodal waist). Girdling constriction of segment IV present, i.e. pre- and postsclerites distinct. Cinctus of abdominal segment IV gutter-like and sculptured, cross-ribbed or not. Abdominal segment IV not conspicuously largest segment. Abdominal tergite IV not folding over sternite, and anterior portions of sternite and tergite equally well visible in lateral view. Girdling constriction between pre- and posttergites of abdominal segments V and VI absent. Girdling constriction between pre- and poststernites of abdominal segments V and VI absent. Pygidium large, with impressed medial field and armed with modified setae and sometimes emarginate to deeply notched. Hypopygium unarmed. Legs: Mid tibia with two pectinate spurs. Hind tibia with two pectinate spurs or with one barbulate and one pectinate spur. Hind basitarsus not widening distally, circular in cross-section. Posterior flange of hind coxa not produced as raised lamella. Metatibial gland absent. Metabasitarsal gland absent. Hind pretarsal claws each armed with a tooth, sometimes very small. Polymorphism: Monomorphic.

Male.Head: Antennae with 13 segments. Clypeus without cuticular apron. Parafrontal ridges present. Torulo-posttorular complex vertical. Maxillary palps unknown. Labial palps unknown. Mandibles triangular, edentate. Ventrolateral margins of head without lamella or ridge extending towards mandibles and beyond carina surrounding occipital foramen. Carina surrounding occipital foramen unknown. Mesosoma: Pronotal flange separated from collar by distinct ridge. Notauli present. Transverse groove dividing mesopleuron present. Propodeal declivity with distinct dorsal edge or margin. Metapleural gland opening present. Propodeal lobes present. Metasoma: Petiole anterodorsally marginate, dorsolaterally immarginate, and laterally above spiracle marginate. Helcium in relation to tergosternal Pronotomesopleural suture placed at posttergite and axial. Prora forming a V-shaped protrusion. Spiracle openings of abdominal segments IV–VI circular. Abdominal segment III more than half size of succeeding segment IV; latter weakly constricted at presegmental portion (uninodal waist). Girdling constriction of segment IV present, i.e. pre- and postsclerites distinct. Cinctus of abdominal segment IV gutter-like and cross-ribbed. Girdling constriction between pre- and postsclerites of abdominal segments V and VI absent. Abdominal segment IV conspicuously largest segment. Abdominal sternite VII simple. Abdominal sternite IX distally armed with two spines, with lateral apodemes about as long as medial apodeme, directed anteriorly (towards head). Genitalia: Cupula long relative to rest of genital capsule and shorter ventrally than dorsally. Basimere broadly fused to telomere, with sulcus discernable at junction, and ventrally with left and right arms separated. Telomere gradually tapering toward apex. Volsella gradually tapering toward apex. Penisvalva laterally compressed, rounded at apex. Legs: Mid tibia with two pectinate spurs. Hind tibia with two pectinate spurs. Posterior flange of hind coxa not produced as raised lamella. Metatibial gland absent. Metabasitarsal glands absent. Hind pretarsal claws each armed with a tooth. Wings: Tegula present, broad, demiovate in shape. Vein C in fore wing present. Pterostigma broad. Abscissa R·f3 present, running toward distal wing margin and enclosing cell with Rs·f5. Abscissae Rs·f2-3 present, connecting with Rs+M&M·f2. Cross-vein 2r-rs present, differentiated from Rs·f4 by presence of Rs·f2-3. Abscissae Rs·f4-5 differentiated into Rs·f4 and Rs·f5 by 2rs-m. Abscissa M·f2 in fore wing present, separated from Rs+M by Rs·f2. Abscissa M·f4 in fore wing present, reaching wing margin. Cross-vein 1m-cu in fore wing present. Cross-vein cu-a in fore wing present, arising from M+Cu and proximal to M·f1. Vein Cu in fore wing present, with both branches Cu1 and Cu2. Vein A in fore wing with abscissae A·f1 and A·f2 present. Vein C in hind wing absent. Vein R in hind wing absent. Vein Sc+R in hind wing present. Abscissa Rs·f1 in hind wing present, shorter than 1rs-m. Abscissa Rs·f2 in hind wing present, not reaching wing margin. Cross-vein 1rs-m in hind wing fused with M·f1. Vein M+Cu in hind wing present. Abscissa M·f1 in hind wing present. Abscissa M·f2 in hind wing present. Cross-vein cu-a in hind wing present. Vein Cu in hind wing present. Vein A in hind wing with abscissae A·f1 and A·f2 present.

Gyne. Alate, similar to worker except for flight-adapted mesosoma. See Terayama et al. (1988) for a description of Cerapachys sauteri gyne.

Larva. Not described. Presence of cocoons unknown.

Distribution.

This rarely collected lineage is represented by at least four extant species of unusual geographic distribution. Chrysapace costatus , Chrysapace crawleyi and Cerapachys sauteri occur in Asia, while an additional, undescribed species has been recently found in northern Madagascar (Brian Fisher pers. comm.). One species is known from Baltic amber.

Taxonomy and phylogeny.

The genus Chrysapace was proposed by Crawley in 1924 for Cerapachys jacobsoni from Sumatra as distinct from the then recognized Cerapachys and Phyracaces . The same year W. M. Wheeler (1924b) published a note where he pointed out that sometime in the future a synonymization of Chrysapace and Cerapachys seems likely, and that this synonymy would render Cerapachys jacobsoni Crawley a junior homonym of Cerapachys jacobsoni Forel, 1912. Wheeler thus proposed a replacement name Chrysapace crawleyi , which was accepted by Brown after he synonymized the genus under Cerapachys in 1975. Cerapachys sauteri Forel from Taiwan was recognized as a relative by Brown based on the original description, and later Terayama et al. (1988) provided a detailed redescription of this species, confirming its affinity with Chrysapace crawleyi . Until recently these two species from Southeast Asia were the only taxa known in this lineage, but the discovery of an undescribed species in Madagascar and the description of Cerapachys costatus from northwest India has significantly broadened the lineage’s known distribution. An additional species of Chrysapace has been recently discovered in Baltic amber ( author’s unpublished observation).

Chrysapace is a member of a well-supported clade that also includes Cerapachys and Yunodorylus , and is possibly the sister genus of Cerapachys although this relationship received less support (Borowiec, in prep.).

Biology.

To the best of my knowledge, nothing on the foraging, nesting, or other aspects of Chrysapace biology has ever been published.

Species of Chrysapace

Chrysapace costatus (Bharti and Wachkoo, 2013): India, comb. n.

Chrysapace jacobsoni Crawley, 1924: Indonesia (Sumatra), nom. rev.

Chrysapace sauteri (Forel, 1913b): Taiwan, comb. n.